An internal combustion engine having a fully flexible valve actuation system is desirable. The ability to control duration, phase, and lift of each engine valve provides an engine designer with tools to achieve benefits measured in emissions, engine performance and fuel economy not readily attainable with conventional valvetrains. While a certain level of flexibility is achievable with cam-based valve actuation systems, e.g., camshaft phasers, multi-profile cams and lifter deactivation, these systems are not able to provide a fully flexible valve control system having a broad range of authority to control valve opening time, duration, and magnitude of lift from fully closed to fully open.
Practitioners have investigated various systems to achieve fully-flexible valve actuation capability, including electromagnetic valve actuation systems. Such systems are camless, but have not been shown to provide variable lift control over full range of valve lift, from fully open to fully closed. Electro-hydraulic valve actuation systems have been proposed and developed for application to internal combustion engines and are capable of providing timing, phasing and fully variable valve lift. Presently known electro-hydraulic valvetrain systems are undesirably large and costly. Furthermore, energy consumption and controllability continue to present challenges to production implementation of such systems.
Therefore, there is a need for a lower cost, readily packageable, electro-hydraulic valve actuation system capable of providing full-range control of engine valve open duration, engine valve open phase relative to the crankshaft, and magnitude of engine valve lift.